Line a 24cm x 30cm baking sheet with a sheet of baking parchment.
Coarsely grate the courgettes . Put the grated courgettes into a mixing bowl, sprinkle with the salt and leave for 45 minutes.
Roll the pastry into a rectangle measuring 24cm x 30cm, then lift on to the parchment-lined baking sheet. Taking care not to cut through to the baking sheet, score a rim on each side of the pastry, 2cm from the edge.
Rest the pastry in the fridge for 25 minutes. Set the oven at 200C/gas mark 6.
Bake the pastry, placing the baking sheet on top of the preheated baking sheet or pizza stone, for about 12 minutes until lightly crisp and gold in colour.
Remove from the oven, then, using the back of a large spoon, press the inner rectangle of pastry all over so it collapses, leaving a raised rim of pastry all round.
In a large mixing bowl, lightly beat the eggs, then pour in the double cream. Add the ricotta and a little seasoning and mix thoroughly, then fold in the crab meat and flour.
Tear or shred the basil leaves then add them to the mixture together with a grinding of black pepper. Salt isn’t necessary.
Gently but firmly squeeze the water from the courgettes, then fold them into the crab custard. Transfer the mixture to the pastry shell, spreading inside the rim of pastry.
Dust the grated parmesan over the surface and bake for 30 minutes or until puffed and golden. Rest for 10 minutes before slicing and serving.